Caption: Ayahuacsa trunk (Banisteriopsis caapi). This vine is native to the tropical forests of South America. Its leaves, and sometimes its bark, are used to prepare a brew of the same name that is used in South American shamanic rituals. It is mixed with plants that contain the compound dimethyltryptamine (DMT), a hallucinogen that is similar in structure to the neurotransmitter serotonin. B. caapi contains harmala, a monoamine oxidase inhibitor that prevents DMT being broken down in the digestive tract. The effects of the ayahuasca brew include altered perception of space and time, hallucinations and euphoria.